The formation of neural connections in the mammalian nervous system is a complex process. During development, axons are initially overproduced and compete for limited quantities of target-derived growth factors. Axons which participate in functional circuits and secure appropriate amounts of growth factors are stabilized, while those axons that are either inappropriately connected or do not obtain sufficient concentrations of growth factors are eliminated in a process termed ‘axon pruning’. In this thesis, I examined the mechanisms that regulate pruning of peripheral, NGF-dependent sympathetic neurons that project to the eye. I determined that pruning of these projections in vivo requires the p75 neurotrophin receptor (p75NTR) and synthesis of brain-derived neurotrophic factor (BDNF) from the activity-dependent exon IV promoter. Furthermore, analysis of an in vitro model of axon competition, which is regulated by the interplay between nerve growth factor (NGF) and neuronal activity, revealed that p75NTR and BDNF are also essential for axon competition in culture. In this model, in the presence of NGF, neural activity confers a competitive growth advantage to stimulated, active axons by enhancing downstream TrkA (NGF receptor) signaling locally in axons. More interestingly, the unstimulated, inactive axons deriving from the same and neighboring neurons acquire a "growth disadvantage" due to secreted BDNF acting through p75NTR, which induces axon degeneration by suppressing TrkA signaling that is essential for axonal integrity. These data support a model where, during developmental axon competition, successful axons secrete BDNF in an activity-dependent fashion which activates p75NTR on unsuccessful neighboring axons, suppressing TrkA signaling, and ultimately promoting pruning by a degenerative mechanism.

The formation of neural connections in the mammalian nervous system is a complex process. During development, axons are initially overproduced and compete for limited quantities of target-derived growth factors. Axons which participate in functional circuits and secure appropriate amounts of growth factors are stabilized, while those axons that are either inappropriately connected or do not obtain sufficient concentrations of growth factors are eliminated in a process termed ‘axon pruning’. In this thesis, I examined the mechanisms that regulate pruning of peripheral, NGF-dependent sympathetic neurons that project to the eye. I determined that pruning of these projections in vivo requires the p75 neurotrophin receptor (p75NTR) and synthesis of brain-derived neurotrophic factor (BDNF) from the activity-dependent exon IV promoter. Furthermore, analysis of an in vitro model of axon competition, which is regulated by the interplay between nerve growth factor (NGF) and neuronal activity, revealed that p75NTR and BDNF are also essential for axon competition in culture. In this model, in the presence of NGF, neural activity confers a competitive growth advantage to stimulated, active axons by enhancing downstream TrkA (NGF receptor) signaling locally in axons. More interestingly, the unstimulated, inactive axons deriving from the same and neighboring neurons acquire a "growth disadvantage" due to secreted BDNF acting through p75NTR, which induces axon degeneration by suppressing TrkA signaling that is essential for axonal integrity. These data support a model where, during developmental axon competition, successful axons secrete BDNF in an activity-dependent fashion which activates p75NTR on unsuccessful neighboring axons, suppressing TrkA signaling, and ultimately promoting pruning by a degenerative mechanism.

Aging is associated with cognitive decline in various domains, including memory. The age-related increase in systemic inflammation has been identified as a potential mechanism contributing to these memory impairments. Specifically, elevated inflammation may impair neurotrophic factor production and function, which is important for maintaining brain health. Physical activity has been identified as a potential strategy for preventing or delaying memory decline, given its ability to reduce inflammation and stimulate neurotrophic factor expression. The present study investigated the relationship between cardiorespiratory fitness, a proxy for habitual physical activity, and memory in older adults. Inflammation and neurotrophic factors were examined as potential mechanisms mediating this relationship. Sixty-five community dwelling older adults (Mage = 70.6 ± 4.0) completed the Rockport 1-mile walk test to predict their cardiorespiratory fitness, as well as the Mnemonic Similarity Task to assess memory. Serum samples were collected to examine inflammatory markers, including interleukin-6 (IL-6), interleukin-1beta (IL-1β), tumor necrosis factor-alpha (TNF-α), and C-reactive protein (CRP), as well as neurotrophic factors, including brain derived neurotrophic factor (BDNF) and insulin-like growth factor-1 (IGF-1). No relationship was found between cardiorespiratory fitness and memory (p > .05). However, older adults with greater cardiorespiratory fitness had lower levels of IL-6 (p < .01) and TNF-α (p < .01) and trended towards higher levels of BDNF (p = .078). Furthermore, IL-6 was negatively correlated with IGF-1 (p < .01), suggesting higher inflammation may impair IGF-1 production. Contrary to our hypotheses, sequential mediation analyses revealed no indirect effect of inflammatory markers and neurotrophic factors on the relationship between cardiorespiratory fitness and memory. Our results suggest that cardiorespiratory fitness may promote favourable changes in inflammatory markers and neurotrophic factors, which—given previous literature—could help to support brain health with advancing age. More research is needed to further examine the relationship between cardiorespiratory fitness and memory. / Thesis / Master of Science (MSc)

The two-hit hypothesis of schizophrenia proposes that the development of the illness involves an early neurodevelopmental stress component which increases vulnerability to later stressful life events, in combination leading to overt disease. This thesis describes a two-hit animal model, comprising of an early first hit in the form of 24 hours maternal deprivation on postnatal day 9, and a late second hit simulated by 2 weeks of corticosterone administration from 8 to 10 weeks of age in rats. The project included behavioural studies on prepulse inhibition (PPI) regulation, locomotor activity, and learning and memory, and neurochemical and molecular studies on dopaminergic parameters, brain-derived neurotrophic factor (BDNF) and glucocorticoid receptor (GR) expression. / In the two-hit animals, there was little effect on baseline PPI or locomotor activity. However, the effect of acute treatment with the dopaminergic stimulants, apomorphine, amphetamine and quinpirole, was markedly diminished. There were differential effects of either maternal deprivation or corticosterone administration on the action of these drugs. However, there was no change in any of the groups in the effect of the serotonin-1A receptor agonist, 8-OH-DPAT, on PPI, or the effect of amphetamine and phencyclidine on locomotor activity. (For complete abstract open document)

abstract: Schizophrenia, a debilitating neuropsychiatric disorder, affects 1% of the population. This multifaceted disorder is comprised of positive (hallucinations/psychosis), negative (social withdrawal/anhedonia) and cognitive symptoms. While treatments for schizophrenia have advanced over the past few years, high economic burdens are still conferred to society, totaling more than $34 billion in direct annual costs to the United States of America. Thus, a critical need exists to identify the factors that contribute towards the etiology of schizophrenia. This research aimed to determine the interactions between environmental factors and genetics in the etiology of schizophrenia. Specifically, this research shows that the immediate early gene, early growth response 3 (EGR3), which is upregulated in response to neuronal activity, resides at the center of a biological pathway to confer risk for schizophrenia. While schizophrenia-risk proteins including neuregulin 1 (NRG1) and N-methyl-D-aspartate receptors (NMDAR’s) have been identified upstream of EGR3, the downstream targets of EGR3 remain relatively unknown. This research demonstrates that early growth response 3 regulates the expression of the serotonin 2A-receptor (5HT2AR) in the frontal cortex following the physiologic stimulus, sleep deprivation. This effect is translated to the level of protein as 8 hours of sleep-deprivation results in the upregulation of 5HT2ARs, a target of antipsychotic medications. Additional downstream targets were identified following maximal upregulation of EGR3 through electroconvulsive stimulation (ECS). Both brain-derived neurotrophic factor (BDNF) and its epigenetic regulator, growth arrest DNA-damage-inducible 45 beta (GADD45B) are upregulated one-hour following ECS in the hippocampus and require the presence of EGR3. These proteins play important roles in both cellular proliferation and dendritic structural changes. Next, the effects of ECS on downstream neurobiological processes, hippocampal cellular proliferation and dendritic structural changes were examined. Following ECS, hippocampal cellular proliferationwas increased, and dendritic structural changes were observed in both wild-type and early growth response 3 knock-out (Egr3-/-) mice. Effects in the number of dendritic spines and dendritic complexity following ECS were not found to require EGR3. Collectively, these results demonstrate that neuronal activity leads to the regulation of schizophrenia risk proteins by EGR3 and point to a possible molecular mechanism contributing risk for schizophrenia. / Dissertation/Thesis / Doctoral Dissertation Neuroscience 2020

Aims: Previous work provided indirect evidence that the neurotrophic factor neurturin (NRTN) is required for normal cholinergic innervation of the heart. This study used nrtn knockout (KO) and wild-type (WT) mice to determine the effect of nrtn deletion on cardiac cholinergic innervation and function in the adult heart. Methods and results: Immunohistochemistry, confocal microscopy, and quantitative image analysis were used to directly evaluate intrinsic cardiac neuronal development. Atrial acetylcholine (ACh) levels were determined as an indirect index of cholinergic innervation. Cholinergic function was evaluated by measuring negative chronotropic responses to right vagal nerve stimulation in anaesthetized mice and responses of isolated atria to muscarinic agonists. KO hearts contained only 35% the normal number of cholinergic neurons, and the residual cholinergic neurons were 15% smaller than in WT. Cholinergic nerve density at the sinoatrial node was reduced by 87% in KOs, but noradrenergic nerve density was unaffected. Atrial ACh levels were substantially lower in KO mice (0.013 ± 0.004 vs. 0.050 ± 0.011 pmol/μg protein; P < 0.02) as expected from cholinergic neuron and nerve fibre deficits. Maximum bradycardia evoked by vagal stimulation was reduced in KO mice (38 ± 6% vs. 69 ± 3% decrease at 20 Hz; P < 0.001), and chronotropic responses took longer to develop and fade. In contrast to these deficits, isolated atria from KO mice had normal post-junctional sensitivity to carbachol and bethanechol. Conclusion: These findings demonstrate that NRTN is essential for normal cardiac cholinergic innervation and cholinergic control of heart rate. The presence of residual cardiac cholinergic neurons and vagal bradycardia in KO mice suggests that additional neurotrophic factors may influence this system.

Schizophrenia (SZ) is a neurological disorder that presents with paranoia, hallucinations, and negative affect. A neurobiological hallmark of SZ is increased dopamine D2 receptor sensitivity. Antipsychotics that treat SZ have demonstrated limited efficacy as well as harmful and sometimes fatal side effects. Additionally, nicotine abuse is greatly increased in individuals diagnosed with SZ compared to the normal population. Treatment of this comorbidity is important, because cigarette smoking diminishes the quality of life in individuals with SZ and shortens their lifespan. The adenosine system is a potential novel target for SZ treatment. Adenosine A2a receptors form a heteromeric complex with dopamine D2 receptors that is mutually inhibitory, meaning each receptor exhibits lower sensitivity to its agonist after the opposing receptor agonist is bound. This study investigated the efficacy of an adenosine A2a agonist, CGS 21680, in alleviating the rewarding aspects of nicotine in the neonatal quinpirole rodent model of SZ. Rats were treated neonatally from postnatal (P)day 1 through 21 with the dopamine D2/D3 agonist quinpirole, raised to P41, and tested on conditioned place preference (CPP). CPP is a behavioral measure of the rewarding properties of a drug through temporal pairing of a drug with a distinct environmental context. Rats were given a drug free pre-conditioning preference test, and then conditioned to saline or nicotine (0.6 mg/kg base) from P43-51. Groups receiving CGS 21680 (0.03 or 0.09 mg/kg) were given the agonist 15 min before nicotine was administered. A drug-free post-conditioning test was administered on P52 to determine preference. The following day, brain tissue was analyzed for brain-derived neurotrophic factor (BDNF) and glial cell-lined neurotrophic factor (GDNF). BDNF is a ubiquitous neurotrophic factor involved in synaptic growth throughout the brain, whereas GDNF is important in dopamine plasticity. Results revealed that neonatal quinpirole enhanced nicotine CPP, replicating previous work, and both doses of CGS 21680 alleviated this enhancement. Nicotine resulted in a CPP in controls, and both doses of CGS 21680 also alleviated this preference. Therefore, CGS 21680 alleviated the rewarding aspects of nicotine. BDNF analyses in the nucleus accumbens (Nacc), a brain area that mediates drug reward, revealed that BDNF closely followed the behavioral results: CGS 21680 alleviated the enhancement in Nacc BDNF in neonatal quinpirole-treated animals, and eliminated the increase in Nacc BDNF produced by nicotine in controls. GDNF analyses revealed that neonatal quinpirole animals conditioned to nicotine resulted in an increase of GDNF in the NAacc, but this was eliminated by CGS 21680. This project revealed that an adenosine agonist with antispsychotic properties may have utility towards decreasing the rewarding aspects of nicotine and its accompanying neural plasticity changes in a model of SZ.

No description available.

A hipermetioninemia é uma condição caracterizada por altos níveis de metionina no sangue e em outros tecidos, podendo causar danos neurológicos, hepáticos e musculares. Considerando que a placenta transfere a metionina do sangue materno para a circulação fetal e que pouco se sabe sobre o efeito da hipermetioninemia gestacional sobre o feto em desenvolvimento, o principal objetivo deste trabalho foi desenvolver um modelo animal de hipermetioninemia materna quimicamente induzido em ratas e utilizar o mesmo para investigar parâmetros bioquímicos (estresse oxidativo, atividade da Mg2+-ATPase, atividade e imunoconteúdo da Na+,K+-ATPase, número de neurônios, níveis de neurotrofinas, metabolismo energético, inflamação e apoptose), moleculares (expressão gênica da Na+,K+-ATPase) e histológicos (microscopia eletrônica) nos encéfalos da prole, bem como avaliar tarefas comportamentais (campo aberto, esquiva inibitória e reconhecimento de objetos). Também analisamos parâmetros de estresse oxidativo/nitrosativo no músculo esquelético e parâmetros de dano muscular e inflamação no soro da prole. A hipermetioninemia foi induzida em ratas através de duas injeções subcutâneas diárias de metionina durante todo o período gestacional. Um grupo de ratas recebeu a dose 1 (1,34 μmol/g peso corporal) e outro recebeu a dose 2 (2,68 μmol/g peso corporal). O grupo controle recebeu salina. Após o nascimento, um grupo de filhotes foi eutanasiado no sétimo dia de vida e outro grupo foi eutanasiado aos 21 dias. Ambas as doses aumentaram os níveis encefálicos de metionina das mães e a dose 2 aumentou os níveis de metionina nos encéfalos da prole. Após estabelecer o modelo, a dose 2 de metionina foi escolhida para estudar os efeitos do tratamento sobre a prole. Os testes bioquímicos subsequentes foram realizados nos filhotes de 21 dias, a histologia foi realizada na prole de 21 e 30 dias e os testes comportamentais foram realizados em filhotes de 30 dias. Os resultados demonstraram que a hipermetioninemia materna reduziu a atividade da Na+,K+-ATPase, Mg2+- ATPase, catalase e complexo II/succinato desidrogenase, o conteúdo de sulfidrilas, número de neurônios e níveis de NGF e BDNF, bem como aumentou os níveis de RNAm e imunoconteúdo da Na+,K+-ATPase nos encéfalos dos filhotes. Foram observados também alterações morfológicas, indicativas de degeneração celular nos neurônios da prole, e os testes comportamentais indicaram deficit de memória. Com relação aos danos musculares, houve um aumento na produção de espécies reativas de oxigênio e lipoperoxidação e uma redução do conteúdo de sulfidrilas, atividades das enzimas antioxidantes e nos níveis de nitritos no músculo esquelético da prole. A atividade da creatina cinase foi reduzida e os níveis de ureia e proteína C reativa foram aumentados no soro. Esses resultados foram acompanhados por perda de massa muscular. Tais achados mostraram que a hipermetioninemia gestacional induziu alterações bioquímicas, moleculares e histológicas no encéfalo e bioquímicas no músculo esquelético e soro dos filhotes, as quais podem contribuir para o entendimento dos mecanismos fisiopatológicos envolvidos nos danos neurológicos e musculares causados por essa condição. Ressaltamos a importância do desenvolvimento do referido modelo de hipermetioninemia gestacional que além de ampliar o entendimento da toxicidade de altos níveis metionina, também abriu perspectivas para novos estudos a respeito dos efeitos ocasionados pela exposição ao excesso de metionina devido a uma condição genética ou uma dieta rica em proteína durante a vida pré-natal. / Hypermethioninemia is a condition characterized by elevated levels of methionine in blood and other tissues and may cause neurological, hepatic and muscular damages. Considering that placenta transfers methionine from maternal blood to the fetal circulation and little is known about the effect of gestational hypermetioninemia on the developing fetus, the main objective of this work was to develop a chemically induced animal model of maternal hypermethioninemia in rats and to use it to investigate biochemical (oxidative stress, activity of Mg2+-ATPase, activity and immunocontent of Na+,K+-ATPase, number of neurons, neurotrophins levels, energy metabolism, inflammation, and apoptosis), molecular (gene expression of Na+,K+-ATPase) and histological parameters (electron microscopy) in encephalon of the offspring, as well as evaluate behavioral tasks (open field, inhibitory avoidance and object recognition). We also analyzed oxidative/nitrosative stress parameters in skeletal muscle and parameters of muscle damage and inflammation in serum of the offspring. Hypermethioninemia was induced in rats through two daily subcutaneous injections of methionine throughout the gestational period. A group of pregnant rats received dose 1 (1.34 μmol/g body weight) and the other received dose 2 (2.68 μmol/g body weight). The control group received saline. After birth, a first group of pups was euthanized at the 7th day of life and the second group at the 21st day of life. Both doses 1 and 2 increased methionine levels in the brain of the mother rats and dose 2 increased methionine levels in encephalon of the offspring. After establishing the experimental model, the highest dose of methionine was chosen to study the effects of treatment on offspring. The subsequent biochemical tests were performed on 21-day-old pups, histological analyses were performed on offspring of 21 and 30 days of age, and behavioral tests were performed on 30-day-old pups. The results demonstrated that maternal hypermethioninemia reduced Na+,K+-ATPase, Mg2+-ATPase, catalase and complex II/succinate dehydrogenase activities, sulfhydryl content, number of neurons and levels of NGF and BDNF, as well as increased levels of mRNA and immunocontent of Na+,K+-ATPase in the brains of the pups. Morphological changes indicative of cellular degeneration were also observed in offspring neurons, and behavioral tests indicated memory deficit. With regard to muscle damage, there was an increase in the production of reactive oxygen species and lipoperoxidation, and a reduction of the sulfhydryl content, antioxidant enzymes activities and in the levels of nitrites in skeletal muscle of the offspring. Creatine kinase activity was reduced and urea and C-reactive protein levels were increased in serum. These results were accompanied by loss of muscle mass. These findings showed that gestational hypermethioninemia induced biochemical, molecular and histological changes in the brain and biochemical changes in skeletal muscle and serum of pups, which may contribute to the understanding of the pathophysiological mechanisms involved in the neurological and muscular damages caused by this condition. We emphasize the importance of the development of this model of gestational hypermetioninemia that, in addition to increasing the understanding of toxicity of high methionine levels, also opened perspectives for new studies regarding the effects caused by exposure to excess methionine due to a genetic condition or a diet rich in protein during prenatal life.

A hipermetioninemia é uma condição caracterizada por altos níveis de metionina no sangue e em outros tecidos, podendo causar danos neurológicos, hepáticos e musculares. Considerando que a placenta transfere a metionina do sangue materno para a circulação fetal e que pouco se sabe sobre o efeito da hipermetioninemia gestacional sobre o feto em desenvolvimento, o principal objetivo deste trabalho foi desenvolver um modelo animal de hipermetioninemia materna quimicamente induzido em ratas e utilizar o mesmo para investigar parâmetros bioquímicos (estresse oxidativo, atividade da Mg2+-ATPase, atividade e imunoconteúdo da Na+,K+-ATPase, número de neurônios, níveis de neurotrofinas, metabolismo energético, inflamação e apoptose), moleculares (expressão gênica da Na+,K+-ATPase) e histológicos (microscopia eletrônica) nos encéfalos da prole, bem como avaliar tarefas comportamentais (campo aberto, esquiva inibitória e reconhecimento de objetos). Também analisamos parâmetros de estresse oxidativo/nitrosativo no músculo esquelético e parâmetros de dano muscular e inflamação no soro da prole. A hipermetioninemia foi induzida em ratas através de duas injeções subcutâneas diárias de metionina durante todo o período gestacional. Um grupo de ratas recebeu a dose 1 (1,34 μmol/g peso corporal) e outro recebeu a dose 2 (2,68 μmol/g peso corporal). O grupo controle recebeu salina. Após o nascimento, um grupo de filhotes foi eutanasiado no sétimo dia de vida e outro grupo foi eutanasiado aos 21 dias. Ambas as doses aumentaram os níveis encefálicos de metionina das mães e a dose 2 aumentou os níveis de metionina nos encéfalos da prole. Após estabelecer o modelo, a dose 2 de metionina foi escolhida para estudar os efeitos do tratamento sobre a prole. Os testes bioquímicos subsequentes foram realizados nos filhotes de 21 dias, a histologia foi realizada na prole de 21 e 30 dias e os testes comportamentais foram realizados em filhotes de 30 dias. Os resultados demonstraram que a hipermetioninemia materna reduziu a atividade da Na+,K+-ATPase, Mg2+- ATPase, catalase e complexo II/succinato desidrogenase, o conteúdo de sulfidrilas, número de neurônios e níveis de NGF e BDNF, bem como aumentou os níveis de RNAm e imunoconteúdo da Na+,K+-ATPase nos encéfalos dos filhotes. Foram observados também alterações morfológicas, indicativas de degeneração celular nos neurônios da prole, e os testes comportamentais indicaram deficit de memória. Com relação aos danos musculares, houve um aumento na produção de espécies reativas de oxigênio e lipoperoxidação e uma redução do conteúdo de sulfidrilas, atividades das enzimas antioxidantes e nos níveis de nitritos no músculo esquelético da prole. A atividade da creatina cinase foi reduzida e os níveis de ureia e proteína C reativa foram aumentados no soro. Esses resultados foram acompanhados por perda de massa muscular. Tais achados mostraram que a hipermetioninemia gestacional induziu alterações bioquímicas, moleculares e histológicas no encéfalo e bioquímicas no músculo esquelético e soro dos filhotes, as quais podem contribuir para o entendimento dos mecanismos fisiopatológicos envolvidos nos danos neurológicos e musculares causados por essa condição. Ressaltamos a importância do desenvolvimento do referido modelo de hipermetioninemia gestacional que além de ampliar o entendimento da toxicidade de altos níveis metionina, também abriu perspectivas para novos estudos a respeito dos efeitos ocasionados pela exposição ao excesso de metionina devido a uma condição genética ou uma dieta rica em proteína durante a vida pré-natal. / Hypermethioninemia is a condition characterized by elevated levels of methionine in blood and other tissues and may cause neurological, hepatic and muscular damages. Considering that placenta transfers methionine from maternal blood to the fetal circulation and little is known about the effect of gestational hypermetioninemia on the developing fetus, the main objective of this work was to develop a chemically induced animal model of maternal hypermethioninemia in rats and to use it to investigate biochemical (oxidative stress, activity of Mg2+-ATPase, activity and immunocontent of Na+,K+-ATPase, number of neurons, neurotrophins levels, energy metabolism, inflammation, and apoptosis), molecular (gene expression of Na+,K+-ATPase) and histological parameters (electron microscopy) in encephalon of the offspring, as well as evaluate behavioral tasks (open field, inhibitory avoidance and object recognition). We also analyzed oxidative/nitrosative stress parameters in skeletal muscle and parameters of muscle damage and inflammation in serum of the offspring. Hypermethioninemia was induced in rats through two daily subcutaneous injections of methionine throughout the gestational period. A group of pregnant rats received dose 1 (1.34 μmol/g body weight) and the other received dose 2 (2.68 μmol/g body weight). The control group received saline. After birth, a first group of pups was euthanized at the 7th day of life and the second group at the 21st day of life. Both doses 1 and 2 increased methionine levels in the brain of the mother rats and dose 2 increased methionine levels in encephalon of the offspring. After establishing the experimental model, the highest dose of methionine was chosen to study the effects of treatment on offspring. The subsequent biochemical tests were performed on 21-day-old pups, histological analyses were performed on offspring of 21 and 30 days of age, and behavioral tests were performed on 30-day-old pups. The results demonstrated that maternal hypermethioninemia reduced Na+,K+-ATPase, Mg2+-ATPase, catalase and complex II/succinate dehydrogenase activities, sulfhydryl content, number of neurons and levels of NGF and BDNF, as well as increased levels of mRNA and immunocontent of Na+,K+-ATPase in the brains of the pups. Morphological changes indicative of cellular degeneration were also observed in offspring neurons, and behavioral tests indicated memory deficit. With regard to muscle damage, there was an increase in the production of reactive oxygen species and lipoperoxidation, and a reduction of the sulfhydryl content, antioxidant enzymes activities and in the levels of nitrites in skeletal muscle of the offspring. Creatine kinase activity was reduced and urea and C-reactive protein levels were increased in serum. These results were accompanied by loss of muscle mass. These findings showed that gestational hypermethioninemia induced biochemical, molecular and histological changes in the brain and biochemical changes in skeletal muscle and serum of pups, which may contribute to the understanding of the pathophysiological mechanisms involved in the neurological and muscular damages caused by this condition. We emphasize the importance of the development of this model of gestational hypermetioninemia that, in addition to increasing the understanding of toxicity of high methionine levels, also opened perspectives for new studies regarding the effects caused by exposure to excess methionine due to a genetic condition or a diet rich in protein during prenatal life.